1. Field of the Invention
The present invention relates to an inclination angle detection device and an inclination angle detection method.
2. Description of the Related Art
An auto-focus camera, etc., comprises a distance-measuring sensor for measuring the distance to a photographic subject. As this kind of distance-measuring sensor, there is a passive method distance-measuring sensor, such as disclosed in Unexamined Japanese Patent Application KOKAI Publication No. 2003-57531 (page 2, page 3, and FIG. 3). As shown in FIG. 22, this kind of passive method distance-measuring sensor comprises a pair of lenses 51a and 51b, and light sensor arrays 52a and 52b. 
The lens 51a and 51b are placed having a distance b. C1 and C2 are center lines of the lens 51a and 51b. The center lines C1 and C2 match with the light ray from a photographic subject 53 that exists in a position which is infinite to the lens 51a and 51b, and are parallel to each other. The light sensor arrays 52a and 52b are placed so that they are respectively vertical to the center lines C1 and C2.
Image data string L0 and R0 of the photographic subject 53 are formed to each of the light sensor array 52a and 52b. In this kind of distance-measuring sensor, the distance from the lenses 51a and 51b to the photographic subject 53 is obtained by Formula 1.
                    L        =                              b            ·            f                                (                          x1              +              x2                        )                                              [                  Formula          ⁢                                          ⁢          1                ]            
When the photographic subject 53 is placed at a position nearer than the position infinite to the lenses 51a and 51b, a phase difference (x1+x2) occurs.
The distance-measuring sensor obtains the correlation function value with a data string L1 and a data string R1 of the light sensor array 51a, while for example shifting the data string R1 on the light sensor 51b. Then, the lag (shift) amount from center lines C1 and C2, wherein the correlation value is local maximum, becomes the phase difference (x1+x2).
The inclination angle of the screen, as the projection surface where the projection light from the projector is projected, can be obtained by applying this kind of distance-measuring sensor to the projector. With the projector, the projection image imaged on the screen is deformed, due to the inclination angle of the screen. Therefore, the inclination angle of the screen towards the optical axis of the projection light of the projector, becomes necessary when adjusting the projection image.
In order to obtain the inclination angle of this kind of screen, the projector is constituted so that the projector comprises the distance-measuring sensor. Then, first, the projector projects chart lights, where bright/dark sections are lined, to the screen, and the distance-measuring sensor receives the reflection light from two distance-measuring windows of the charts that are projected. Next, the projector respectively measures the phase difference, in cases where reflection light is received from the two distance-measuring windows, and measures the distances to a plurality of distance-measuring points on the screen, based on the respectively obtained phase difference. If distance-measuring data to the plurality of distance-measuring points on the screen can be obtained, the inclination angle of the screen can be obtained based on this distance-measuring data.
However, with an inclination angle detection device using this kind of distance-measuring sensor, even if the distances to the plurality of distance-measuring points on the screen is measured, the detected distances change, if the projection position of the charts is slightly displaced. Therefore, even if the inclination angle of the screen surface is obtained by the detected distance, the inclination angle can not be obtained with high accuracy.